A strain sensor has a cylindrical strain body extending along the axial direction, a first fixed part, a second fixed part, and a strain detection element. The first fixed part is connected to the strain body at a first connection part and extends in the axial direction from an opening of a first end of the strain body. The first fixed part has a first engagement part fixed to a subject. The second fixed part is connected to the strain body at a second connection part and extends from an opening of a second end of the strain body in a direction opposite from that of the first fixed part so that there is a space between the second fixed part and the strain body. The second fixed part has a second engagement part fixed to the subject. The strain detection element is provided on the outer circumferential surface of the strain body. The strain detection element is disposed so that the center of the strain detection element in the axial direction is closer to the second fixed part than the center of the space.
